1. Any IDE hard drive will work, but only 4GB can be supported "out of the box". Drives of any larger size need a patch to scsi.device (yes, even though it's an IDE controller) and a patch to the FastFileSystem. TD64 is a keyword to search for.
2. The A1200 can only take 8MB with the original 68EC020 CPU. Better chips in the 68K series can take more. Depending on the acclerator, up to 256MB can be added.
3. The PCMCIA card must be 16bit (not CardBus) and support 5V power. Make sure it's supported by cnet.device or 3c589.device (see
Aminet.
4. Yeah, it's annoying isn't it? Back then, things were expensive because they were new, expensive technology. Now they're expensive because demand far exceeds supply.